Now that the door glitch has been patched the best way in my opinion is to have one lure while the rest hides and only comes out to shoot the bosses. Although it makes lockdown easier, it doesn't guarantee your succes, so don't play with people that don't know what to do.

Lure spots for normal rounds

Door 1 and 2:
Stand on the edge near room 3

Door 1 and 3:
Stand on the edge near the vent at room 2

Door 2 and 3:
Same as door 1 and 2 lure but the others have to cover the lure from the prisoners from door 3

Door 1, 2 and 3:Stqnd on the spot of door 1 and 2 while one or two of your teammates keep killing the spawns from room 3. The other teammate(s) cover(s) the back at the stairway.

Luring in boss rounds

Rounds when bosses spawn in waves:

All people go to closest room of door 3 and wait while all bosses have
spawned while killing the blue guy that keeps spawning. When all bosses
have spawned one guy of your team needs to get out there and start
circling the bosses while the others shoot from above. If you are
luring, I find the best way to get started is to run down the stairs,
behind the pillar at the boxes and then start circling. Whe you have
started circling, make sure the bosses dont lose their view on you or
they will switch targets and start shooting your team. In other words
don't run behind the pillar at the boxes again, nor run into the
u-shaped room.

For lockdown extreme, round 13 and 26:

Start circle luring immediately while the others hide in the stairway
till all bosses are drawn to the lure, then the others can start
shooting them from above.

I would gladly give a full playthrough vid of Lockdown extreme using these tactics, but the problem is that AVA regurlarly crashes in coop modes nowadays, making it impossible to finish Lockdown extreme.

However here is a video of the lure spots and tactics in use to get you started.

Rewards for Lockdown:

The only things you can be sure of when getting a reward in Lockdown is:26 boxes in lockdown extreme will get you silver deagle for 30 days or in less occasions you will get a clan mask for 30 days. Other than that, rewards can vary from getting euros to stuff like lucky shot armor that you can buy for euros, viper mask, mag upgrades, ST camo, deagle for fewer than 30 days, etc...

For normal difficulty, you got a slight chance of getting a deagle and other rewards.

For easy difficulty, you usually get euro rewards which are rather small, although I have gotten 500 euro and lucky shot armor a few times while trying to solo it.If I could I would make a nice overview of the rewards but since the rewards are either random or have to do with your playing prestation in the game, it is hard to make that overview.